Although there have been many significant contributions to the study of insect immunity, the mechanisms underlying the cellular immune reactions of insects have never been clearly established. The fundamental problems that are in need of immediate study are similar to those problems faced by vertebrate immunologists and include 1) cellular proliferation, differentiation and migration, and 2) the specificity of cell interactions. The major objective of the proposed research is to obtain information on the mechanism(s) of recognition of foreignness by cells. Insect cells provide a model for the study of cellular responses during infection. The specific aims of the proposal are 1) to determine whether the cellular immune responses of insects are activated by hormonal imbalances during parasitization by internal matazoan parasites, and 2) to identify the chemotactic substance(s) produced during infection causing hemocytes to leave areas of the body where they are normally found and to encapsulate parasites. The methods of study of possible hormonal changes and effects include neck ligation and topical application of hormones, and biochemical analyses. Chemotactic behavior and comparative quantitative hemocytological studies will be made with phase microscopy.